1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.functor.core.comparator;
18
19 import java.io.Serializable;
20 import java.util.Comparator;
21
22 import org.apache.commons.functor.BinaryPredicate;
23 import org.apache.commons.functor.UnaryPredicate;
24 import org.apache.commons.functor.adapter.RightBoundPredicate;
25
26 /**
27 * A {@link BinaryPredicate BinaryPredicate} that {@link #test tests}
28 * <code>true</code> iff the left argument is less than or equal to the
29 * right argument under the specified {@link Comparator}.
30 * When no (or a <code>null</code> <code>Comparator</code> is specified,
31 * a {@link Comparable Comparable} <code>Comparator</code> is used.
32 *
33 * @version $Revision: 1166346 $ $Date: 2011-09-07 21:48:07 +0200 (Wed, 07 Sep 2011) $
34 * @author Rodney Waldhoff
35 */
36 public final class IsLessThanOrEqual<T> implements BinaryPredicate<T, T>, Serializable {
37
38 /**
39 * Basic IsLessThanOrEqual instance.
40 */
41 public static final IsLessThanOrEqual<Comparable<?>> INSTANCE = IsLessThanOrEqual.<Comparable<?>>instance();
42
43 /**
44 * serialVersionUID declaration.
45 */
46 private static final long serialVersionUID = -7270189005780457145L;
47
48 private final Comparator<? super T> comparator;
49
50 /**
51 * Construct a <code>IsLessThanOrEqual</code> {@link BinaryPredicate predicate}
52 * for {@link Comparable Comparable}s.
53 */
54 @SuppressWarnings("unchecked")
55 public IsLessThanOrEqual() {
56 this(ComparableComparator.INSTANCE);
57 }
58
59 /**
60 * Construct a <code>IsLessThanOrEqual</code> {@link BinaryPredicate predicate}
61 * for the given {@link Comparator Comparator}.
62 *
63 * @param comparator the {@link Comparator Comparator}, when <code>null</code>,
64 * a <code>Comparator</code> for {@link Comparable Comparable}s will
65 * be used.
66 */
67 public IsLessThanOrEqual(Comparator<? super T> comparator) {
68 if (comparator == null) {
69 throw new IllegalArgumentException("Comparator argument must not be null");
70 }
71 this.comparator = comparator;
72 }
73
74 /**
75 * {@inheritDoc}
76 * Return <code>true</code> iff the <i>left</i> parameter is
77 * less than or equal to the <i>right</i> parameter under my current
78 * {@link Comparator Comparator}.
79 */
80 public boolean test(T left, T right) {
81 return comparator.compare(left, right) <= 0;
82 }
83
84 /**
85 * {@inheritDoc}
86 */
87 public boolean equals(Object that) {
88 return that == this || (that instanceof IsLessThanOrEqual<?> && equals((IsLessThanOrEqual<?>) that));
89 }
90
91 /**
92 * Learn whether another IsLessThanOrEqual is equal to this.
93 * @param that the IsLessThanOrEqual to test.
94 * @return boolean
95 */
96 public boolean equals(IsLessThanOrEqual<?> that) {
97 if (null != that) {
98 if (null == comparator) {
99 return null == that.comparator;
100 }
101 return comparator.equals(that.comparator);
102 }
103 return false;
104 }
105
106 /**
107 * {@inheritDoc}
108 */
109 public int hashCode() {
110 int hash = "IsLessThanOrEqual".hashCode();
111 // by construction, comparator is never null
112 hash ^= comparator.hashCode();
113 return hash;
114 }
115
116 /**
117 * {@inheritDoc}
118 */
119 public String toString() {
120 return "IsLessThanOrEqual<" + comparator + ">";
121 }
122
123 /**
124 * Get a typed IsLessThanOrEqual instance.
125 * @param <T>
126 * @return IsLessThanOrEqual<T>
127 */
128 public static <T extends Comparable<?>> IsLessThanOrEqual<T> instance() {
129 return new IsLessThanOrEqual<T>();
130 }
131
132 /**
133 * Get an IsLessThanOrEqual UnaryPredicate.
134 * @param right the right side object of the comparison.
135 * @return UnaryPredicate
136 */
137 public static <T extends Comparable<?>> UnaryPredicate<T> instance(T right) {
138 return RightBoundPredicate.bind(new IsLessThanOrEqual<T>(), right);
139 }
140
141 }